After days of talks in Qatar, a new umbrella group representing the forces outside and inside Syria that are pitted against President Bashar Assad finally emerged. In the 20 months that the Syrian civil war has raged--killing more than 30,000 people and spilling into neighboring countries--foreign powers sympathetic to the rebel cause have remained frustrated by the opposition's internal dissension. Western and Arab backers of the rebellion hope that the new opposition leadership will finally become the foundation of a credible, inclusive alternative to the Assad regime. On Nov. 13,...